- Integrins and laminin are crucial for morphogenesis of the kidney tubular epithelium. During development, integrins interacting with laminin and other extracellular matrix proteins are essential for epithelial-mesenchymal interactions, polarization of the early epithelium, and differentiation of individual cell types along the nephron. In the adult, integrins anchor cells to the basal lamina composed of different laminin isotypes. Disruption of these interactions together with depolarization of integrins are important steps in the pathogenesis of acute renal failure and other disease processes. As the tubular epithelium regenerates, integrins and laminin are undoubtedly major factors in the ensuing redifferentiation. In this part of the project, the investigators propose to continue studies on the roles of integrins and extracellular matrix proteins in kidney morphogenesis. In particular, experiments are designed to increase an understanding of integrin function during injury, regeneration, and differentiation of kidney tubular epithelial cells at the molecular level. In Specific Aim 1, an examination of the modulation of integrin ligand-binding activity, expression, and distribution in kidney cell lines subjected to ATP-depletion will be carried out. In addition, basolateral targeting signals in integrins will be identified, and the distribution of integrin alpha and beta subunits in the ischemic rat kidney will be examined. In Specific Aim 2, the role of Forssman antigen in laminin adhesion, cell polarization, and morphogenesis will be examined through reconstitution studies, biological assays, and antisense approaches. The expression of laminin isotypes in kidney cell lines during tubulocyst formation and after mechanical injury, and in the post-ischemic rat kidney will also be determined. Finally, the involvement of integrins and laminin in epithelial cell polarization will be tested through the expression of antisense and dominant-negative constructs.